Cher's naked dress, Princess Diana in a slip and Alexander McQueen's tartan ensemble: Why the Met Gala is regarded as the 'Superbowl of Fashion'

Once upon a time, the Met Gala was a simple midnight supper held to raise money for the then-struggling Costume Institute. So how did a dinner with a $50 entry fee morph into the celebrity circus that takes over every first Monday in May?